1. Field of the Disclosure
The present disclosure relates to a glass substrate that is coated with multiple coating layers, in order to give the coated substrate the ability to reflect infrared wavelength in targeted ranges. More particularly, the present disclosure relates to four, five, and six-layered coatings on the glass substrate, where the coatings comprise one or more metal oxides and optional dopants.
2. Description of the Related Art
Current heat reflective coatings on glass are typically designed for 400 nm to 1200 nm or 5000 nm to 50,000 nm wavelengths, which are primarily visible light applications or long wavelength IR, lower temperature applications, respectively. For example, such coatings would be used on architectural windows to keep heat out or heat in, depending on the climate in which they were used. These coatings have limited performance when used for heat reflection in the range from 1000 nm to 5000 nm, or 5000 nm to 21,000 nm, which is the infra-red light range.
Some current multi-layered coatings are primarily used in the interior surfaces of multi-pane insulated glass windows in order to avoid exposure to an atmosphere other than an inert gas, such as argon. These coatings can't be used in heated appliance applications due to rapid coating degradation. Some reflectivity exists in the range from 700 nm to 1200 nm, but it is not optimized, as the application is for prevention of solar heat transmission through glass in hotter climates.
Existing single layer pyrolytic coatings are limited and have only one heat reflective surface. The second surface of the substrate is not coated, or if it is coated, sputtered coatings are typically applied. These coatings are typically optimized for 10,000 nm to 50,000 nm wavelengths. Some reflectivity exists in the range from 5000 nm to 10000 nm, but it is not optimized, as the application is typically for prevention if heat loss through glass in cold climates.
Existing single layer pyrolytic coatings that are produced on two sides simultaneously, or in one-pass serial production processes, are limited in that they can only be optimized for heat reflective applications by way of an increased coating thickness. However, the durability and performance of thicker coatings degrades due to a mismatch in expansion characteristics between the glass substrate and the coating. To prevent this, the overall thickness of the coating layers does not exceed 350 nm. Either way, these single layer coatings do not provide for improved reflectivity in the 1000 nm to 2500 nm range and only limited improvement in the 2500 nm to 5000 nm range.
Some existing multi-layered pyrolytic coatings also consist of a sub-layer with limited or no heat reflecting properties, and the surface layer which is heat reflecting. Overall coating thickness limitations prevent the surface layer from being fully optimized for the purpose of heat reflection in the 1000 nm to 5000 nm range.
There is a need to address these deficiencies, and for a coated glass substrate that can be customized to reflect light in the ranges of 1000 nm to 5000 nm, and from 5000 nm and 21000 nm.